High temperature resistant polymers, e.g. as measured by heat distortion temperature and/or glass transition temperature (Tg), are especially useful for a variety of high value, high performance applications. Among the polymers which commonly find use in such applications are thermoset polymers such as epoxy, phenolic and imide polymers. For many applications thermoplastic polymers having high performance temperature such as polyetherimides, polyetherketones, ploysulfones and polyamideimides are preferred because they are processable into articles by conventional thermoplastic molding methods. However, such high performance temperature thermoplastic polymers are typically characterized by one or more disadvantageous properties such as high cost arising from complex preparation methods, high dielectric permittivity, high moisture absorption. Despite their inherent disadvantages the high performance temperature thermoplastic polymers are materials for choice for many applications.
French Brevet d'invention 1,594,934 and U.S. Pat. No. 3,959,234 disclose a variety of norbornene dicarboximide polymers exhibiting a wide range of Tg from -172.degree. C. to 189.degree. C. depending on the hydrocarbon radical forming the imide group as indicated in the following Table 1.
TABLE 1 ______________________________________ Imide Group Radical Tg, .degree.C. ______________________________________ methyl 185/189 ethyl 169 n-propyl 149 iso-propyl 180 n-butyl 149 t-butyl 177 n-hexyl 40 n-octyl -32 n-decyl -43 cyclohexyl -172 benzyl 152 phenyl 162/166 ______________________________________
High performance temperature thermoplastic polymers of N-methyl norbornene dicarboximide polymers having a Tg greater than 200.degree. C. are disclosed in my prior United States application Ser. No. 07/196,992. Polymers of N-methyl norbornene dicarboximide can be simply prepared, e.g. by melt polymerization using conventional metathesis polymerization catalysts, and exhibit favorable dielectric permittivity, e.g., about 3.1 after equilibrating in room temperature air at 50% relative humidity. However, they exhibit disadvantageously high moisture absorption, e.g. more than 6% weight gain after equilibrating in boiling water for 7 hours.
Other high performance temperature thermoplastic polymers of N-phenyl norbornene dicarboximide polymers having a Tg greater than 200.degree. C. are disclosed by me in U.S. Pat. No. 4,965,330. Although polymers of N-phenyl norbornene dicarboximides exhibit low moisture absorption, e.g. about 3% after equilibrating in boiling water, they unfortunately are not as simple to prepare, e.g. the precursor monomer is not amenable to melt polymerization because it has a high melt temperature. Preparation of the polymer by solution polymerization, e.g. in chlorinated hydrocarbon solvents, is undesirable because of cost and environmental burdens.
An object of this invention is to provide a novel high temperature performance polymers that can be prepared by simple polymerization methods, i.e. melt polymerization, and that exhibit desirably low dielectric permittivity and moisture absorption.